You love space. You love physics and science and rockets and Mars and things like that. You work with a bunch of other people who at least like what they do, because they certainly aren't there for the money.

Cons

The pay is pretty bad, the benefits pretty terrible also, and NASA still uses twenty year old computers and Windows XP for development and realtime OS work. It's pretty pathetic, and doesn't hold a candle to proper software development companies in terms of computing hardware.